Well folks I have a question about f ratio. I understand how you work out what the ratio of a particular scope is, eg. Focal length/ primary diameter in mm. I believe that the lower the ratio the more light is let through, and to use some terminology, the faster a scope is.
If I am understanding correctly, the lower the f ratio of a scope, the less exposure time is needed for photography. If I am correct in this assumption, it stands to reason therefore, the faster a scope is the more detailed its views will be at a particular magnification when viewing at the ep. (more light in the same amount of time hitting your eye).
My question is, if the above statements are correct, then wouldn't the best viewing scope be the one that is fastest?
I understand that there would be a certain focal length that would be too short for any given scope, because then you couldn't possibly get the required maginification to see smaller objects. I guess I am trying to understand why a cassegrain for eg. (hope thats how you spell it) has such long focal lengths for a given arpeture. If my statements above are correct, then wouldn't it be better to have a shorter focal length?
I know there must be reasons for it, but would like to know what they are. I also would like to know these answers because I will be upgrading to a larger scope some time in the near future, and would like to take f ratio into account when i decide which to get.
thanks for listening. hope its not a dumb question.